1. Field of the Invention
The present invention relates to an earplug and more specifically is directed to an injection molded resilient thermoplastic elastomer (TPE) earplug having at least one flange and useful as a hearing protector.
2. Description of the Prior Art
There are presently on the market a number of earplugs that include a central shaft and extending there from at a nose end at least a single flange. The earplugs are generally composed of an injection molded resilient thermoplastic elastomer material such as synthetic rubber material. The flange element extends outwardly from the nose end of the shaft member and also extends rearward from the nose end and is so spaced so as to provide a free annular space between the flange and the shaft. One basic earplug of this type is generally referred to as the V-51R earplug and was developed during the course of World War II in order to provide improved hearing protection to members of the military who were subjected to excessive sound.
In use, the earplug is forcibly inserted into the ear canal, thereby at least partially collapsing the rearward extending flange element into the underlying free annular space and conforming the flange element into an acoustic sealing relationship to the walls of the ear canal.
Three of the important criteria for any earplug of this type, in addition to sound attenuation, are ease of insertion into the ear canal, comfort during use and ease of removal when appropriate. In general, softer polymers are more comfortable in use for obvious reasons and harder materials, while less comfortable, are easier to insert into the ear canal.
An improved triple flange version of this type of earplug is shown in U.S. Pat. No. 4,867,149 listing Robert N. Falco as the inventor and issued on Sep. 19, 1989. This patent gives further background information on the V-51R earplug and other prior art earplugs of this type. In addition U.S. Pat. No. Des 253,723 issued on Dec. 18, 1979 listing Howard S Leight as the inventor, also shows a triple flange earplug, which is currently on the market.
The prior art earplugs of the type disclosed above typically have a number of problems. For example, the earplug shown in U.S. Pat. No. 4,867,149 has a solid shaft member to support the multiple flanges and this type of earplug can create discomfort in a significant proportion of the wearer population. This discomfort would generally be perceived as a sense of excessive pressure being brought to bear on the walls of the ear canal because of the central solid shaft member not flexing adequately to the curvature of the car canal. The central solid shaft member, however, does have the advantage of allowing the earplug to be fully inserted into the ear canal as long as the material used to make the earplug of the U.S. Pat. No. 4,867,149 is of a sufficient hardness to allow for this full insertion.
The product on the market made in accordance with U.S. Pat. No. Des. 253,723 are generally of a softer material than the product made in accordance with the U.S. Pat. No. 4,867,149. In addition the product made in accordance with the U.S. Pat. No. Des. 253,723 is hollow at the tip and therefore is more comfortable in the ear. However, since the product made in accordance with the U.S. Pat. No. Des. 253,723 is of a softer material, it is difficult to insert this earplug fully into the ear since the rear end of the earplug does not have sufficient stiffness for the user to fully insert the earplug into the ear.
It would therefore be desirable to have an earplug, which is comfortable in the ear, includes at least a single flange member and yet has sufficient rigidity at a rear end portion to enable the user to fully insert the earplug into the ear. U.S. Pat. No. 5,957,136 overcomes the problems of the above prior art earplugs by using a two-piece construction. This construction includes front and rear members. One member, located at the rear, forms part of the shaft of the earplug. This rear member is made of a relatively hard polymeric material to aid in inserting the earplug into the ear canal. The other front member forming the earplug is made of a relatively soft resilient material so as to be comfortable within the interior of the ear. The forward end of the earplug has a bulbous outer configuration and with at least one flange located rearward of the bulbous end so as to have a tighter sealing relationship with the walls of the earplug.
This two-piece construction increases the cost of the earplug since the separate pieces must be separately injection molded and must then be assembled to form the earplug. The combination of the two materials requires additional labor and handling in manufacturing and thereby increases the cost relative to a one-piece earplug injection molded out of a single material. It would be desirable to achieve the benefits of the earplug of U.S. Pat. No. 5,957,136 without the added cost of molding and assembly.